Energetics of Alkali and Alkaline Earth Ion-Exchanged Zeolite A

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• 作者：Hui Sun ; Di Wu ; Kefeng Liu ; Xiaofeng Guo ; Alexandra Navrotsky
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：July 21, 2016
• 年：2016
• 卷：120
• 期：28
• 页码：15251-15256
• 全文大小：372K
• 年卷期：0
• ISSN：1932-7455

文摘

Alkali and alkaline earth ion-exchanged zeolite A samples were synthesized in aqueous exchange media. They were thoroughly studied by powder X-ray diffraction (XRD), electron microprobe (EMPA), thermogravimetric analysis and differential scanning calorimetry (TG-DSC), and high temperature oxide melt solution calorimetry. The hydration energetics and enthalpies of formation of these zeolite A materials from constituent oxides were determined. Specifically, the hydration level of zeolite A has a linear dependence on the average ionic potential (Z/r) of the cation, from 0.894 (Rb-A) to 1.317 per TO₂ (Mg-A). The formation enthalpies from oxides (25 °C) range from −93.71 ± 1.77 (K-A) to −48.02 ± 1.85 kJ/mol per TO₂ (Li-A) for hydrated alkali ion-exchanged zeolite A, and from −47.99 ± 1.20 (Ba-A) to −26.41 ± 1.71 kJ/mol per TO₂ (Mg-A) for hydrated alkaline earth ion-exchanged zeolite A. The formation enthalpy from oxides generally becomes less exothermic as Z/r increases, but a distinct difference in slope is observed between the alkali and the alkaline earth series.